Changes

Summary

1. more informative error for spurious crash;
2. merged
3. tuned;
4. dummy File_Watcher for Windows (spurious crashes seen on Windows 7);
5. more robust treatment of logical lines;
6. updated package;
7. proper name for recursive grammar; pro-forma update of fileTypes;
8. emit Commands_Changed for blobs as well, e.g. relevant for isabelle.vscode.Server.prover_output;
9. suppress empty results;
10. tuned;
11. manage document blobs as well;
12. misc tuning and clarification;
13. tuned;
14. tuned;
15. tuned;
16. tuned structure
17. lead_coeff is more appropriate as abbreviation
18. more lemmas; tuned headings
19. covering space lift lemmas
20. facts about ANRs, ENRs, covering spaces
21. New theory of arcwise connected sets and other new material
22. connectedness, circles not simply connected , punctured universe
23. New material about path connectedness, etc.
24. tuned NEWS
25. reworked to provide auxiliary operations Euclidean_Algorithm.* to instantiate gcd etc. for euclidean rings
26. moved euclidean ring to HOL
27. reshaped euclidean semiring into hierarchy of euclidean semirings culminating in uniquely determined euclidean divion